The present invention relates to a pressure and temperature reactor vessel, especially a multi-autoclave and to details concerning the design of this equipment.
Many materials, such as e.g. zeolites, are prepared by so-called hydrothermal synthesis at temperatures ranging from 100xc2x0 C. to 200xc2x0 C. requiring crystallization times of one hour or more. For syntheses being carried out at temperatures that are higher than the solvent""s boiling point, it is necessary to use pressure vessels, and these have to be suitable for the temperature and pressure used during the operation. The pressure vessel has to be designed so that the handling of it does not represent any unnecessary hazard, provided it is used according to working instructions.
Zeolite syntheses are usually performed in strongly alkaline media, often at pH greater than 14, and the reaction mixture will often contain toxic chemicals, such as e.g. fluoride. Conventionally, syntheses that may be performed at temperatures lower than 110xc2x0 C. are carried out in polymer bottles, often Teflon, while reactions at higher temperatures require steel autoclaves, perhaps lined with Teflon. The price of an autoclave of this type with the required safety details are typically of the order of NOK 10,000 or higher. Furthermore, such an autoclave will weigh from 1 kilogram and upwards, and all these elements represent limitations regarding the number of syntheses that may be performed in most laboratories in the course of one year.
Zeolite synthesis is often carried out by keeping the synthesis mixture at around 100xc2x0 C. for at least 6 hours. At these moderate temperatures sealed chambers are necessary in order to avoid drying out of the synthesis mixture.
As an example of conventional zeolite synthesis, Zeolite Y can be prepared according to U.S. Pat. No. 3,130,007, Example 1, by dissolving 5 g sodium aluminate containing 30 weight percent Na2O and 44 weight percent Al2O3 and 22 g sodium hydroxide containing 77.5 weight percent Na2O in 89.5 ml distilled water. This solution was added to 124.2 g of an aqueous colloidal silica solution with 29.5 weight percent SiO2, so that the resulting mixture had a composition corresponding to 13.9 Na2O: Al2O3: 28.2 SiO2:471 H2O, and the mixture was homogenized by stirring. The mixture was enclosed in a sealed glass vessel, placed in a water bath and heated at 100xc2x0 C. for 21 hours, after which the product was recovered by filtering, washed and dried. Common to all the synthesis procedures mentioned and for all other known synthesis procedures for preparation of zeolites on a laboratory scale with the purpose of discovering new zeolites or to optimize existing zeolites, is that these are performed in a cumbersome and expensive manner by having to separately prepare each reaction mixture, which typically consists of 4-7 reagents, and by adding the reagents one by one.
In many other examples the synthesis of zeolites and other molsieves need temperatures well above 100xc2x0 C., so that steel pressure vessels or the like are required.
Furthermore, each reaction mixture is typically prepared in batches of 5 to 100 g and crystallized in expensive and heavy autoclaves with internal volumes often in the range of 25 to 250 ml and with weights of up to 8 kg per autoclave, causing considerable expense due to a large consumption of often expensive reagents and due to the fact that the handling of the heavy autoclaves often makes it impossible to handle more than one autoclave at the time, and finally that the size of the autoclaves limits the number of autoclaves that may be placed in each oven or heating unit The combination of all these elements are, according to known technology, making each zeolite synthesis a very resource intensive process, and there is a great need for greater efficiency, rationalization, downscaling and automation. Simple calculations have shown that by combining the different variables which are involved in zeolite synthesis with narrow enough intervals in reagent concentrations, temperatures, reaction time, etc. to cover any phase formation based on known examples, it is feasible to make up 1018 recipes. With today""s synthesis capacity, which on a global basis hardly exceeds 100,000 syntheses per annum, it would take 10,000,000,000,000 years to carry out all these syntheses in which each and every one in theory has potential for the preparation of a new zeolite or other microporous material. The expenses involved in performing these syntheses according to known technology would obviously be formidable, and there is thus a great need for new and more cost efficient methods for zeolite synthesis.
In recent years new, automated methods for systematic preparation of new compounds, so-called xe2x80x9ccombinatorial techniquesxe2x80x9d, have been developed, but equipment which may be used for liquid phase synthesis at temperatures above approximately 100xc2x0 C. has til now not been disclosed, because this requires that the synthesis takes place in a hermetically sealed vessel at elevated pressures. WO 95/12608-A1 for instance, discloses an apparatus and a method for a) synthesis of several molecules on substrates, comprising distribution of the substrates in the reaction chambers, b) combination of the first addition of these molecules with different reagents in each of the reaction chambers, c) moving the substrates through tubing to separate mixing chambers where the substrates are mixed, d) redistribution of the substrates by transporting them through tubing back to the reaction chambers, and e) combination of a second portion of a different composition with the first portions of molecules in the different reaction chambers in order to prepare new mixtures. This publication describes only a system for mixing and distribution of different molecules and not a system for hermetical sealing of the reaction chambers which would make it possible to operate at high temperatures, and this system would thus not be suitable for the synthesis of zeolites. In WO 96/11878 there is a description of extensive use of a combinatorial arrangement for synthesis of new materials, including zeolite synthesis at 100xc2x0 C. Even though this patent application presents a detailed description of instrumentation and equipment developed for different purposes, autoclave systems required for performing the syntheses under the prevailing physical conditions (elevated pressure and temperatures exceeding 100xc2x0 C.) are not described.
The prior art teaches autoclaves with several chambers for special purposes, and there is for instance in U.S. Pat. No. 5,505,916 a description of a metal cassette which can be opened and closed like a suitcase, and which has an interior with compartments intended for placement of the different instruments used by dentists, where these may be sterilized by autoclaving. Furthermore, large autoclaves intended for instance for the growth of crystals, are known, and examples are described in U.S. Pat. No. 5,322,591, U.S. Pat. No. 5,312,506 and U.S. Pat. No. 5,476,635, but the purpose of these and similar autoclaves is to make it possible to carry out large-scale syntheses, for which there is a great need when a synthetic procedure has been established and scale-up is desired, or when the purpose is to grow single crystals as large as possible. The autoclave described in the earlier mentioned U.S. Pat. No. 5,312,506 is designed to withstand temperatures up to 1500xc2x0 C. for growth of crystals from metal melts. Another feature in connection with work with autoclaves is energy savings, and this is addressed in EP 0.434.890 A1, with description of a system for insulation of the autoclave walls and for the design of such insulating layers in the walls, which could be useful for large-scale autoclaving, but is of no relevance when working with small laboratory autoclaves which are heated in ovens.
Furthermore, there is a series of known equipment intended for synthesis of proteins and biopolymers, where the design comprises sheets with a large number of chambers intended for screening of syntheses and crystal growth, and in its simplest form as described in U.S. Pat. No. 5,096,676 and U.S. Pat. No. 5,400,741 describes a diffusion cell for growth of the largest and the most perfect crystals possible of macromolecular compounds by a technique called the xe2x80x9changing dropxe2x80x9d technique. Several patents, e.g. U.S. Pat. No. 5,013,531, U.S. Pat. No. 5,531,185, U.S. Pat. No. 5,362,325 and EPA 0.553.539 A1, deal with cells for growth of proteins and biopolymer crystals in spacecrafts. Common for the latter patents is that the designs described are very sophisticated and thus very expensive, because they are intended for use in spacecrafts. Common for all equipment designed for synthesis and crystal growth of proteins and biopolymers is that they are meant for use at low temperatures, or typically temperatures in the range of 0xc2x0 C. to 65xc2x0 C., and that they consequently are not designed to withstand conditions typical for hydrothermal synthesis. In addition, many of these prior art synthesis cells are not lined with Teflon or other similarly inert materials, something that almost without exceptions is required for synthesis of zeolites and the like. There is, e.g., a known design called xe2x80x9cmultiblockxe2x80x9d (Yrchnak, V., Vagner, J.; Peptide Res. 3, 182 (1990)) consisting of i) a Teflon block holding 42 reactors, polypropylene syringes equipped with polymer filters, ii) a vacuum adapter connecting each reactor to a vacuum line (not described in detail) which enables rapid washing in an apparatus for continuous flow, iii) two Teflon plates with 42 stoppers to which the Teflon block is fastened during use, and iv) a glass cover used during homogenization. The problem with this design is that the reactors which are made of glass and which do not have protected sidewalls may be used only at low pressures and not in strongly alkaline solutions. There is thus no available literature describing equipment that might be used for practical work with combinatorial zeolite synthesis, in as much as such syntheses almost without exception require hydrothermal treatment of a solution or gel with a relatively high content of water and often high contents of organic compounds in a closed chamber, and almost all methods for preparation of zeolites known so far require such conditions during synthesis. This is true without exception for all methods which have proved to be commercially applicable. The synthesis of zeolites is thus normally performed under hydrothermal conditions which require elevated pressures and high temperatures during periods up to several weeks without leakage. The problem has so far been the costs involved in this type of work, estimated to an average of NOK 5,000 per synthesis, including recovery of the product and XRD analysis. An important feature when dealing with large series of syntheses is therefore how the product can be recovered and washed in a rational way without insurmountable expense, something that is not disclosed in prior art. As far as is known, this type of work is performed in the same manner by all synthesis laboratories engaged in synthesis of zeolites and non-carbon-based molecular sieves.
One objective of the present invention has been to develop a complete system for screening of synthesis conditions for preparation of zeolites and other non-carbon materials requiring hydrothermal conditions in the temperature range 100xc2x0 C. to 250xc2x0 C. in a more cost efficient manner, and it has thus been of interest to improve a series of parameters, which means making them more cost efficient Some of these parameters are:
1. Reduced size of the separate reaction chambers and increased number of reaction chambers, which is called a multi-autoclave. This will lead to reduced use of reactants and thus cheaper synthesis.
2. Automated addition of reactants, for instance by having 100 reaction chambers present in one multi-autoclave and by enabling this to be connected to a pipetting machine which makes quick and exact addition of all liquid reactants possible.
3. Simple and easy-to-use mechanism for the closing and opening of the multi-autoclave.
4. Simple recovery and washing of the synthesis product and simple cleaning of the multi-autoclave after use.
5. Devices allowing automated analysis with X-ray diffraction and automatic identification of known crystalline phases by combination of an automatic sample switcher, a structure library stored in a database and software that can monitor sample switching and identification.
Another objective of the present invention described here has been to design automated equipment for larger synthesis series and prepare formulations based on mixtures of different liquids/solutions with varying reactant ratios.
These and other objectives are attained by the present invention, which represents a break-through in terms of cost reduction for zeolite synthesis in that the reaction mixture crystallizes in a volume reduced typically to {fraction (1/100)} of what has been used conventionally, thereby achieving reduced consumption of reactants and cheaper syntheses, and further by enabling automated addition of reactants, e.g. by having 100 or more available reaction chambers in one single multi-autoclave. The multi-autoclave plates can be connected to a pipetting machine that makes quick and exact addition of all liquid reactants possible, and several such plates with reaction chambers can be placed on top of each other without difficulty. Furthermore, an important feature of the present invention is the simple and not very time-consuming operation of the multi-autoclave.
The present invention relates to a pressure and temperature reactor vessel i.e. a multi-autoclave, comprising
a) a central block having a multitude of perforations, wherein the perforations are through-going perforations, cavities or another form of hole permanently closed at one end,
b) a cover member, operatively associated with a sealing member, for engagement with the central block to seal the open ends of the perforations to form a multitude of chambers,
c) a sealing member, operatively associated with the cover member to form a pressure tight seal when the cover member is brought into position by a locking device, and
d) a locking device acting in concert with the cover member to engage the sealing member so as to define a multitude of reaction chambers.
Applications for the present invention may, in addition to zeolite synthesis, be in any field of activities within research and development connected to products where at least one production step comprises the mixing of different liquids, e.g. in the fields of organic and inorganic syntheses, paint production, formulation of fuels, food industry, etc., and, furthermore, applications can include clinical testing or dissolution and digestion of samples with acid etc., where a liquid reactant is added to a liquid or solid. The invention is in particular aimed at applications where open vessels cannot be used, and more specifically for applications where it is required to operate at temperatures which will cause elevated pressures in the liquid part of the mixture.